FUN:
PRANK YOUR PARENTS. EVERYDAY!
PRANK YOUR TEACHER!
SCARE YOUR BROTHER!

ANTI-THEFT:
PREVENT EVIL ROOMMATES FROM READING YOUR MESSAGES
PREVENT INTRUDERS FROM ACCESSING YOUR PHONE

Open the app, turn the screen off and put it on the table. After 2.5 seconds it'll enter the Lurking state.
Anyone that moves it even slightly or tries to open it will be scared to death by a real horror scream.

You can use their phone to download the app, start it and then turn off the screen.... and wait!

Turn on PRANK MODE to make the app disappear after you turn off the screen, so whoever first picks up the phone won't know what happened or what app caused the scream!

Don't forget to turn the Notification/Media volume (Not the Ringtone) UP in your settings for 100% guaranteed efficiency!